Wall sensors and scanners, such as stud finders, are well-known and commonly used by tradesmen and do-it-yourselfers in construction projects to locate objects located below the surface of a wall. One type of stud finder is a single mode electronic stud finder, which typically includes a capacitor for detecting changes in the capacitance as the stud finder moves across the surface of the wall. A change in capacitance indicates that the dielectric constant of the surface has changed due to the presence of an object behind the surface of the wall.
In addition to single mode wall scanners, multifunction detection units have been developed which can be toggled between various modes of detection. For example, in addition to the circuitry described above, a stud finder might include separate circuitry for detecting metal behind a wallboard and for detecting an AC voltage behind a wallboard to determine whether the wall has a live wire behind it. An AC voltage detector may alert the user to the location of electrical wiring in the wall and could prevent the user from cutting into the wire. Alternatively, an AC voltage detector could aid the user in finding the wire if the user is performing electrical work.
Electrical outlet testers are another commonly used tool for electrical work. These devices are typically self-contained, and designed to be plugged into a standard electrical outlet having hot, neutral, and ground connections to determine whether the outlet is properly wired. These devices allow the wiring of an electrical outlet to be verified easily, without the need for meters or other devices.
Certain construction projects involving electrical work require both a detection unit and an electrical outlet tester. For example, installing a new outlet requires that the tradesman determine the location of existing electrical outlets and wall studs, wire the new outlet, and ensure that the outlet is correctly wired. If the outlet includes a ground fault circuit interrupter, it requires testing. However, the need for two separate tools creates a problem because the user needs to (1) buy two separate tools, and (2) actually find each tool when he or she wants to use them.